1. Field of the Invention
The invention relates to a method of producing a rare earth magnet using hot working. “Hot working” has substantially the same meaning as “hot plastic working”.
2. Description of Related Art
Rare earth magnets, as typified by neodymium magnet (Nd2Fe14B), have a very high magnetic flux density and are used for various applications as strong permanent magnets.
It is known that a neodymium magnet has higher coercivity as its crystal grain size is smaller. Thus, a magnetic powder (powder particle size: approximately 100 μm), which is a nano-polycrystalline material with a crystal grain size of approximately 50 to 100 nm, is filled in a mold and hot press working is performed to form a bulk body with the nano-polycrystalline structure maintained. In this state, however, the individual nano-crystal grains are randomly oriented and high magnetization cannot be obtained. Thus, hot working for crystal alignment should be performed to induce crystal gliding to align the orientation of the crystal grains.
For example, Japanese Patent No. 2693601 discloses a method of producing a rare earth magnet by performing cold molding, hot press consolidation, and hot working on an R—Fe—B alloy (wherein R represents at least one rare-earth element including Y) powder that is obtained by melt quenching. However, there is a limit to the improvement of magnetization because there is a limit to the resulting degree of crystal orientation.